The science regarding the structure, formation and evolution of stars.
Questions tagged [stellar-physics]
180 questions
65
votes
3 answers
Why is the Sun almost perfectly spherical?
Relatively recent measurements indicate that the Sun is nearly the roundest object ever measured. If scaled to the size of a beach ball, it would be so round that the difference between the widest and narrow diameters would be much less than the…
user81619
57
votes
4 answers
Why does a supernova explode?
This is really bugging me. When you look up some educational text about stars life, this is what you find out:
Gravity creates the temperature and pressure to start fusion reactions.
The fusion proceeds to heavier and heavier cores ending with…
Tomáš Zato
- 3,103
36
votes
2 answers
Can a neutron star become a black hole via cooling?
How much does thermal expansion affect neutron stars? Would the loss of temperature cause a neutron star to be more densely packed and thus collapse into a black hole?
user289661
- 916
30
votes
5 answers
Why is the Sun called an "average star"?
This is a statement (presumably in mass, longevity, energy output) many people that I've met have heard in school, and it is known in pop culture. However, according to Wikipedia, about 75% of the stars in the universe are red dwarfs, which greatly…
Ovi
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28
votes
5 answers
Can elements heavier than iron be present in a star's core?
My understanding is that elements heavier than iron and nickel are not formed in a star but, can heavy elements such as lead and others be present/found in a star's core ?
I ask because the following document…
ScienceAmateur
- 381
25
votes
4 answers
Where will the Goldilocks zone be when the Sun becomes a red giant?
In about 5 billion years, when our Sun expands into a red giant making our planet uninhabitable, where will the new Goldilocks zone be? Could life form on a new planet in the Goldilocks zone? Environment suitable for human life?
Ubelt6
- 251
23
votes
2 answers
Why is the cut off mass for massive stars 8 solar masses? Why can't it be 10-11 solar masses or so?
I know that stars having a mass greater than or equal to 8 solar masses are termed "massive stars". But why is the cut-off 8 solar masses?
Rian
- 425
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21
votes
4 answers
How can a star emit light if it is in Plasma state?
I understand that star is in Plasma state (all nucleus and electrons are not bound to each other and moving around freely)
Photon is emitted when an excited electron moves back to lower orbit.
So in a star if electrons are not in any orbit then how…
user45246
- 247
19
votes
1 answer
Why is the Sun made of light elements only?
Since the entire solar system inherits its heavy elements from supernovae unrelated to our star, I fail to understand why, while capturing most of said system's matter, the sun only contain light elements, especially hydrogen, selecting out heavy…
Winston
- 3,276
19
votes
5 answers
How is hydrostatic pressure overcome when a star is formed?
If stars are formed by the collapse of dust clouds under gravity, how is the pressure of the dust cloud overcome?
As more material gathers together, gravity will increase, but pressure will also increase. If I am not mistaken, both will increase as…
user2800708
- 962
17
votes
7 answers
What is the easiest way to stop a star?
On long enough cosmological time scales, hydrogen and helium nucleii will become scarce in the Universe. It seems to me that any advanced civilisations that might exist in that epoch would have the motivation to try and prevent the stars from using…
N. Virgo
- 35,274
14
votes
1 answer
What proportion of a star's hydrogen is consumed in its life?
I've heard in a lecture that a star like the sun would burn 3% of its Hydrogen before expiring.
I would have thought it would be much more.
zeristor
- 376
13
votes
2 answers
What is the Sun's core made of?
The obvious answer is hydrogen and helium plasma but the nuclear fusion can also create heavier elements. Are these heavier elements a significant portion of the core? Do the heavier elements "sink" to the "bottom" of the core, like iron has during…
dave
- 387
12
votes
1 answer
Can a gas cloud of pure helium collapse and ignite into a star?
Assuming there could be a giant gas cloud with negligible amount of hydrogen and metal (elements with atomic number $Z\geq3$), could it collapse gravitationally and form a pure helium star that would skip the main sequence entirely?
I think it's…
Jasmeru
- 1,178
11
votes
2 answers
Why are there spectral lines at all?
My somewhat basic understanding of the concept comes from lectures I've attended about the Bohr-model, which explains the phenomenon as arising from the fact that certain configurations of an atom can only absorb certain wavelengths of light and…
Andreas Hagen
- 556